Routers are gateway devices, and are used to connect networks that are logically separated, e.g., local area networks, wide area networks. Routers have been widely used in various trades, and have become important devices to implement connections within a backbone network, between backbones and between a backbone and an Internet. Data transmission from a subnet to another subnet can be implemented through routing functions of the routers. The routers have functions of determining network addresses and selecting IP paths, which enables them to establish flexible connections in a multi-networking environment. In the multi-networking environment, the routers can use different data grouping methods and media access methods to connect various subnets.